1. Field of the Invention
The present invention relates to a liquid crystal display (LCD) device, and more particularly, to a multi-domain LCD device and method of fabricating the same.
2. Discussion of the Related Art
Demands for various display devices have increased with development of an information society. Accordingly, many efforts have been made into research and development of various flat display devices such as liquid crystal displays (LCD), plasma display panels (PDP), electroluminescent displays (ELD), and vacuum fluorescent displays (VFD). Some types of flat display devices have already been incorporated into various equipments.
Among the various flat display devices, liquid crystal display (LCD) devices are most widely used due to advantageous characteristics such as high picture quality, thin profile, light weight, and low power consumption. Accordingly, the LCD devices are considered good substitutes for cathode ray tubes (CRT). In addition to mobile type LCD devices such as a display for a notebook computer, LCD devices have been adapted to function as computer monitors and televisions for receiving and displaying broadcast signals. In order to use LCD devices as general displays for various applications, key characteristics considered are whether the LCD devices can provide a high quality picture, such as high resolution and high luminance having a large-sized screen, while still maintaining light weight, thin profile, and low power consumption.
In general, an LCD device includes a liquid crystal panel for displaying images and a driver circuit for applying a driving signal to the liquid crystal panel. The liquid crystal panel includes first and second glass substrates bonded to each other with space therebetween that is occupied by a liquid crystal layer, usually formed by injection.
The first glass substrate (referred herein as a TFT array substrate) includes a plurality of gate lines arranged along a first direction at fixed intervals, a plurality of data lines arranged along a second direction perpendicular to the first direction at fixed intervals, a plurality of pixel electrodes formed in a matrix arrangement at pixel regions where the gate lines cross the data lines, and a plurality of thin film transistors (TFTs) switched by signals of the gate lines to transfer signals of the data lines to each pixel electrode. The second glass substrate (referred herein as a color filter substrate) includes a black matrix layer that blocks light from regions other than the pixel regions, color filter layers for displaying various colors, and a common electrode for producing the image.
The aforementioned LCD device is driven based on optical anisotropy and polarity characteristics of the liquid crystal layer. Since liquid crystal molecules of the liquid crystal layer are thin and long, the liquid crystal molecules have particular alignment characteristics. An alignment direction of the liquid crystal molecules is controlled by an induced electric field applied thereto. Accordingly, light irradiated through the liquid crystal layer may be controlled by altering the alignment direction of the liquid crystal molecules, thereby displaying an image.
FIG. 1 illustrates a plane view illustrating a multi-vertical alignment (MVA) mode LCD device according to a related art, and FIG. 2 illustrates a structural sectional view taken along line I˜I′ of FIG. 1. As shown in FIG. 1 and FIG. 2, a lower substrate 10 of the related art MVA mode LCD device includes a plurality of gate lines 11 arranged along a first direction, a plurality of data lines 12 arranged along a second direction perpendicular to the first direction at fixed intervals to define pixel regions, a thin film transistor (TFT) array 16 including thin film transistors formed at regions where the gate lines cross the data lines, and pixel electrodes 13 formed in the pixel regions, having one or more slits 15 spaced apart from one another at a predetermined interval.
An upper substrate 20 of the related art MVA mode LCD device includes a black matrix layer (not shown) to cover portions other than the pixel regions, R/G/B (red/green/blue) color filter layers 22 formed corresponding to the pixel regions, and a common electrode 23 formed on an entire surface of the upper substrate including the color filter layers 22. Boss shaped dielectric patterns 21 are formed on opposing sides of the slits 15.
In the related art MVA mode LCD device, liquid crystal molecules 30 having negative dielectric anisotropy is used. When voltages are applied to the related art MVA mode LCD device, an electric field is formed between the common electrode 23 and the pixel electrode 13. The liquid crystal molecules 30 are aligned in accordance with the electric field. Thus, the liquid crystal molecules 30 are aligned obliquely to a horizontal plane as shown in FIG. 2. Distortion of the electric field occurs between the upper and lower substrates 20 and 10 as the dielectric patterns 21 and the slits 15 are interposed between the substrates. The electric field formed is represented as dotted lines along the equivalent potential as shown in FIG. 2. The liquid crystal molecules 30 are aligned in a direction transverse to the equivalent potential lines. Accordingly, the slits 15 and the dielectric patterns 21 serve as the boundary between domains where the alignment direction of the liquid crystal molecules is varied.
FIG. 3 is a graph illustrating transmittance per portions of elements shown in FIG. 2. As shown in FIG. 2, the liquid crystal molecules 30 are aligned by the slits 15 and the dielectric patterns 21 without rubbing. When the driving voltage is applied to the pixel electrode 13, the electric field is not normally formed in a portion corresponding to the slits 15. For this reason, the liquid crystal molecules 30 are not aligned. The liquid crystal molecules 30 are confined in a portion corresponding to the dielectric patterns 21 due to distortion of the electric field. As a result, regions around the slits 15 and the dielectric patterns 21 have low transmittance. These low transmittance portions deteriorate luminance.
Furthermore, the slits 15 and dielectric patterns 21 may each have a small width to prevent reduction of transmittance. However, in this case, the electric field effect per domain is suppressed to reduce transmittance of the whole LCD panel and response characteristics of the liquid crystal layer. Therefore, the slits and dielectric patterns have fixed minimum widths.